The first object was to secure the sea.
The Roman fleet, which during the campaign in Greece was charged with the task of interrupting the communication between Greece and Asia Minor, and which had been successful about the time of the battle at Thermopylae in seizing a strong Asiatic transport fleet near Andros, was thenceforth employed in making preparations for the crossing of the Romans to Asia next year and first of all in driving the enemy's fleet out of the Aegean Sea.

It lay in the harbour of Cyssus on the southern shore of the tongue of land that projects from Ionia towards Chios; thither in search of it the Roman fleet proceeded, consisting of 75 Roman, 24 Pergamene, and 6 Carthaginian, decked vessels under the command of Gaius Livius.

The Syrian admiral, Polyxenidas, a Rhodian emigrant, had only 70 decked vessels to oppose to it; but, as the Roman fleet still expected the ships of Rhodes, and as Polyxenidas relied on the superior seaworthiness of his vessels, those of Tyre and Sidon in particular, he immediately accepted battle.

At the outset the Asiatics succeeded in sinking one of the Carthaginian vessels; but, when they came to grapple, Roman valour prevailed, and it was owing solely to the swiftness of their rowing and sailing that the enemy lost no more than 23 ships.

During the pursuit the Roman fleet was joined by 25 ships from Rhodes, and the superiority of the Romans in those waters was now doubly assured.